So I found a problem in some new housings on a motor I just rebuilt for a customer... The trailing spark plug hole on one of the BRAND NEW rotor housings is not tapped through all the way. The first plug I went to put in started to get tight, and I backed it out, and went again. After doing this twice I inspected the plug and noticed that the threads were being crushed. Son of a gun. Now I have to tap into a motor I just rebuilt and make sure EVERY precaution is taken to avoid getting ANY tap shavings in the motor.
Has anyone else had this problem, or have any advice for me when tapping it out?

 

lots of grease on the end of the tap and only take a little bit at a time, thats what i did after the previous owner of my car decided the spark plug should go in at a 45 degree angle.

 

Get a spark plug thread chaser and see if that will clean it up some for you.....

 

put a lot of vasaline on the tap, and tap it slowwwly. backing out every full turn. All the chips should stick to the vasaline. Just wipe it clean and add new vasline after every turn. Should work out fine...

 

Seems you would need a BOTTOM tap to do this. Not just any old threaded tap that's tapered.

 

If the engine is still on a stand tap it with the sparkplugs facing down so shavings will fall out rather than in.

 

Update;
So after I special ordered a tap from my local industrial supply store, and I got it taken care of.
First I practiced on a used housing to see if the tap I had would work and go all the way through without doing damage to the far wall. It was fine and I was able to do it with a regular tapeder tap and did not have to use a bottom tap. I was able to find a tapered vaccume cap and put it in while I did the dirty work. I used ALOT of grease on the end of the tap and worked VERY SLOWLY only going about 1 full turn each time and cleaning and replacing the grease every time. Once this was done I cleaned and cleaned again and installed a NEW spark plug since the threads were ruined on the other one. All done.
Now I have the tap I will be checking new housings BEFORE I do the rebuilds and install the motor lol.
Thanks for the advice guys!
-Robert

 

I wouldn't think it's a worry as the compression stroke is shielded from any vacuum INTO the chamber through the plugs. in other words, it doesn't suck through the plugs like a piston engine would.

GD

 

I have to admit there is something fishy about this post or I have a REAL bad memory. How can you use a tapered tap to tap allllll the way thru the housing?????? Stock trail sparkplug holes do not go ALLLLLLL the way thru the housing. Like I said, memory thing here. Ain't no waaaaay according to my memory that the trail holes go all the waaaay thru the housing.

Bad memory here???????? Possible I guess. That's the reason I mentioned BOTTOM tap 'cause no waaaay a tapered tap could do the job.

EDIT: Clarification. I mean the hole goes all the way thru, just not the sparkplug threads. I need to go look at a housing I guess.

Attached is the only rotor housing jpg I have, but if you look closely, you can see the lead and trail sparkplug hole diameter on the rotor side of the rotor housings are different in size. Trail MUCH smaller exit hole. I doubt threads go thru all the way.

The words and numbers written on the jpg are MEANINGLESS to this post. Not related at all.

 

You're correct in that the trailing plug hole is restricted, and smaller than the leading:

 

Yes the upper/trailing hole is smaller. Couple of weeks ago I added Sea Foam to my engine to try and save it from a rebuild. Bottom/leading hole was much easier to use because it is larger.

 

I should clarify. The tapered went far enough in for the spark plug threads to thread in all the way...The hole going into the combustion chamber was left alone... Make since?..

 

Ok.

 

Thank you for your input HAILERS. It is alway appriciated, and you are a great help on this forum!

 

Good problem solving. But I have to admit that this is the first time I ever heard of a housing that wasn't tapped. Unicorn? I hope so.

Good work.